Anchoring Inserts, Electrode Assemblies, and Plasma Processing Chambers

ABSTRACT

A showerhead electrode is provided where backside inserts are positioned in backside recesses formed along the backside of the electrode. The backside inserts comprise a threaded outside diameter, a threaded inside diameter, and a tool engaging portion formed in the threaded inside diameter. The tool engaging portion is formed such that the backside insert further comprises one or more lateral shielding portions between the tool engaging portion and the threaded outside diameter to prevent a tool engaged with the tool engaging portion of the backside insert from extending beyond the threaded outside diameter of the insert. Further, the tool engaging portion of the backside insert comprises a plurality of torque-receiving slots arranged about the axis of rotation of the backside insert. The torque-receiving slots are arranged to avoid on-axis rotation of the backside insert via opposing pairs of torque-receiving slots.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.12/409,984, filed Mar. 24, 2009, entitled “ANCHORING INSERTS, ELECTRODEASSEMBLIES, AND PLASMA PROCESSING CHAMBERS” (LAR P1694X IA), which is acontinuation-in-part of U.S. patent application Ser. No. 12/251,997,filed Oct. 15, 2008 (LAR P1694 PA).

This application is related to but does not claim priority to U.S.application Ser. No. 12/112,112 (LAR P1678X IA), filed Apr. 30, 2008,entitled “ELECTRODE ASSEMBLY AND PLASMA PROCESSING CHAMBER UTILIZINGTHERMALLY CONDUCTIVE GASKET AND 0-RING”; U.S. application Ser. No.12/050,195 (LAR P1745 PA), filed Mar. 18, 2008, entitled “ELECTRODEASSEMBLY AND PLASMA PROCESSING CHAMBER UTILIZING THERMALLY CONDUCTIVEGASKET”; and U.S. application Ser. No. 13/409,527 (LAR P1694 NA), filedMar. 1, 2012, entitled “SHOWERHEAD ELECTRODES”.

BACKGROUND

The present disclosure relates generally to plasma processing and, moreparticularly, to plasma processing chambers and electrode assembliesused therein. Plasma processing apparatuses can be used to processsubstrates by a variety of techniques including, but not limited to,etching, physical vapor deposition, chemical vapor deposition, ionimplantation, resist removal, etc. For example, and not by way oflimitation, one type of plasma processing chamber contains an upperelectrode, commonly referred to as a showerhead electrode, and a bottomelectrode. An electric field is established between the electrodes toexcite a process gas into the plasma state to process substrates in thereaction chamber.

BRIEF SUMMARY

According to one embodiment of the present disclosure, a showerheadelectrode is provided where backside inserts are positioned in backsiderecesses formed along the backside of the electrode. The showerheadelectrode can be a single-piece, circular showerhead or amulti-component, circular showerhead which can include a circularcentral electrode and one or more peripheral electrodes arranged aboutthe circumference of the central electrode. The backside insertscomprise a threaded outside diameter, a threaded inside diameter, and atool engaging portion formed in the threaded inside diameter. The toolengaging portion is formed such that the backside insert furthercomprises one or more lateral shielding portions between the toolengaging portion and the threaded outside diameter to prevent a toolengaged with the tool engaging portion of the backside insert fromextending beyond the threaded outside diameter of the insert.

In another embodiment, the tool engaging portion of the backside insertcomprises a plurality of torque-receiving slots arranged about the axisof rotation of the backside insert. The torque-receiving slots arearranged to avoid on-axis rotation of the backside insert via opposingpairs of torque-receiving slots.

Additional embodiments relate to plasma processing chambers comprisingshowerhead electrodes fabricated in the manner disclosed herein.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description of specific embodiments of thepresent disclosure can be best understood when read in conjunction withthe following drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 is a schematic illustration of a plasma processing chamberincorporating particular aspects of some embodiments of the presentdisclosure;

FIG. 2 is a plan view of the backside of a showerhead electrodeaccording to one embodiment of the present disclosure;

FIG. 3 is a cross-sectional illustration of a portion of a showerheadelectrode according to one embodiment of the present disclosure;

FIG. 4 is an isometric illustration of the backside and thicknessdimensions of a showerhead electrode according to one embodiment of thepresent disclosure;

FIG. 5 is a cross sectional illustration of an electrode assemblyincluding securing hardware according to one embodiment of the presentdisclosure;

FIGS. 6, 7, 8A, and 9 are cross sectional illustrations of a portion ofan electrode assembly including securing hardware according to somealternative embodiments of the present disclosure;

FIGS. 8B and 8C are schematic illustrations presented to clarify thestructure and operation of the subject matter illustrated in FIG. 8A;

FIGS. 10 and 11 illustrate securing hardware and complementary machinedportions of an electrode assembly according to a further alternativeembodiment of the present disclosure;

FIGS. 12 and 13 are isometric illustrations of a backside insertaccording to an additional aspect of the present disclosure;

FIGS. 14 and 15 are schematic illustrations of two alternative ways toarrange torque-receiving slots in a backside insert according to thepresent disclosure; and

FIG. 16 is an isometric illustration of a tool for engaging and rotatingthe backside insert illustrated in FIGS. 12 and 13.

DETAILED DESCRIPTION

The various aspects of the present disclosure can be illustrated in thecontext of a plasma processing chamber 10, which is merely illustratedschematically in FIG. 1 to avoid limitation of the concepts of thepresent disclosure to particular plasma processing configurations, orcomponents, that may not be integral to the subject matter of thepresent disclosure. As is generally illustrated in FIG. 1, the plasmaprocessing chamber 10 comprises a vacuum source 20, a process gas supply30, a plasma power supply 40, a substrate support 50 including a lowerelectrode assembly 55, and an upper electrode assembly 100.

Referring to FIGS. 2-5, an upper electrode assembly 100 according to oneembodiment of the present disclosure is illustrated. Generally, theelectrode assembly 100 comprises securing hardware 60, alignment pins66, a thermal control plate 70, a showerhead electrode 80, and athermally conductive gasket 75 positioned between the frontside 74 ofthe thermal control plate 70 and the backside 82 of the showerheadelectrode 80. More specifically, the thermal control plate 70 comprisesa backside 72, a frontside 74, and one or more process gas passages 76configured to direct process gas to the frontside 74 of the thermalcontrol plate 70. Although the present disclosure is not limited toparticular thermal control plate materials or process gas passageconfigurations, it is noted that suitable thermal control platematerials include aluminum, aluminum alloys, or similar thermalconductors. In addition, it is noted that a variety of teachings may berelied upon in the design of thermal control plates including, but notlimited to, U.S. Pub. No. 2005/0133160.

The showerhead electrode 80 comprises a backside 82, a frontside 84, anda plurality of showerhead passages 86 extending from the backside 82 ofthe showerhead electrode 80 to the frontside 84 of the showerheadelectrode 80. The showerhead electrode 80 further comprises a pluralityof backside recesses 88 formed in the backside 82 of the electrode 80.As is illustrated in FIG. 5, the backside recesses 88 leave a thicknessx of electrode material between the recess 88 and the frontside 84 ofthe electrode 80. Backside inserts 90 are positioned in the backsiderecesses along the backside 82 of the electrode 80. The electrodematerial between the recess 88 and the frontside 84 of the showerheadelectrode 80 helps minimize potential source of contamination in theplasma processing chamber 10 by isolating the backside inserts 90 andthe securing hardware 60 from reactive species in the plasma chamber. Tohelp ensure that the aforementioned isolation can be maintained over thelife of the electrode 80, the thickness x is preferably at leastapproximately 0.25 cm or, stated differently, at least approximately 25%of the total thickness of the showerhead electrode 80.

Referring to FIG. 1, this isolation can be enhanced by configuring thethermal control plate 70 and the showerhead electrode 80 to define ahermetically sealed plasma partition 65 such that gas and reactivespecies within the evacuated portion 15 of the plasma processing chamber10 cannot reach the securing hardware 60 and the inserts. The particularmanner in which the plasma partition 65 is defined will vary dependingon the respective configurations of the thermal control plate 70 and theshowerhead electrode 80. It is contemplated that in most cases, therespective materials forming the thermal control plate 70 and theshowerhead electrode 80 will define the majority of the partition. Inaddition, it is contemplated that a variety of sealing members can beused to enhance the partition, particularly where the thermal controlplate 70 and the showerhead electrode 80 interface with each other andwith other components of the plasma processing chamber 10.

Referring to FIG. 5, the aforementioned isolation of the backsideinserts 90 and the securing hardware 60 from reactive species in theplasma processing chamber 10 can be further enhanced by positioning thebackside inserts 90 in the backside recesses 88 such that they are insetor, at least, flush relative to the backside 82 of the showerheadelectrode 80. Similarly, the securing hardware 60 can be positioned insecuring hardware passages 78 in the thermal control plate 70 such thatit is inset or, at least, flush relative to a backside 72 of the thermalcontrol plate 70.

In addition to the process gas passages 76, the thermal control plate 70comprises securing hardware passages 78 that are configured to permitsecuring hardware 60 to access the backside inserts 90 positioned in thebackside recesses 88 along the backside 82 of the showerhead electrode80. The thermal control plate 70 and the showerhead electrode 80 can beengaged using the securing hardware 60 and the backside inserts 90. Inthe engaged state, the frontside 74 of the thermal control plate 70faces the backside 82 of the showerhead electrode 80 and the showerheadpassages 86 in the showerhead electrode 80 are aligned with the processgas passages 76 in the thermal control plate 70. In addition, thesecuring hardware passages 78 are aligned with the backside inserts 90positioned in the backside recesses 88 along the backside 82 of theelectrode 80. As a result, the securing hardware 60 may extend throughthe securing hardware passages 78 in the thermal control plate 70 andengage the backside inserts 90, which are positioned in the backsiderecesses 88 along the backside 82 of the electrode 80.

The securing hardware 60 and the backside inserts 90 are configured tomaintain engagement of the thermal control plate 70 and the showerheadelectrode 80. In addition, the securing hardware 60 and the backsideinserts 90 are configured to permit disengagement of the thermal controlplate 70 and the showerhead electrode 80. In the embodiment illustratedin FIG. 5, and other embodiments described herein, the electrodematerial of the showerhead electrode 80 is isolated from frictionalcontact with the securing hardware 60 by the relatively resilientmaterial of the backside inserts 90 during engagement and disengagement.This isolation, provided by the backside inserts 90, serves to eliminateabrasion of the electrode material by the securing hardware 60 as asource of contamination in the plasma processing chamber 10. Theresiliency of the backside inserts 90 also permit repeated,nondestructive engagement and disengagement of the thermal control plate70 and the showerhead electrode 80.

Although a variety of materials may be selected to form the backsideinserts 90, including thermoplastics or other kinds of plastics,synthetic rubbers, ceramics, metals, or inserts with composite layers ofmaterials, according to some embodiments of the present disclosure, thebackside inserts comprise significant amounts of polyetheretherketone(PEEK) formulated and manufactured such that the hardness of thebackside inserts 90 does not exceed the hardness of the electrodematerial. Additional candidate materials include, but are not limited toDelrin® or other acetal resin engineering plastics formulated as filledor unfilled homopolymers or copolymers, nylon, polytetrafluoroethylene(PTFE), or combinations thereof.

Although the thermal control plate 70 and the showerhead electrode 80can be engaged in a variety of ways consistent with the concepts of thepresent disclosure, in the embodiments illustrated in FIGS. 5, and 7-11,the backside inserts 90 can be configured as anchors in the backsiderecesses 88 formed in the backside 82 of the showerhead electrode 80.More specifically, in the embodiment of FIG. 5, the backside insert 90is anchored in the backside recess by providing a threaded portion inthe electrode material. With the insert 90 in place, the securinghardware 60, which may for example comprise a threaded screw or bolt,engages the backside insert 90 to secure the showerhead electrode 80 tothe thermal control plate 70. In the embodiment of FIG. 7, the backsideinsert is anchored in the backside recess via a bonding agent. In theembodiment illustrated in FIGS. 8A-8C, the backside recess 88 ismachined to comprise an undercut portion 89 and the backside insert 90is anchored in the backside recess 88 by inserting the insert 90 intothe recess 88 and rotating it into the undercut portion 89 of thebackside recess 88.

Referring to FIG. 9, it is noted that the backside insert 90 can beconfigured as a stud comprising a backside extension 92 that isconfigured to extend into one of the securing hardware passages 78 inthe thermal control plate 70. In which case, the securing hardware 60 isconfigured to access the backside extension 92 of the backside insert 90in the securing hardware passage 78 via, for example, a threadedengagement.

In any of the embodiments disclosed herein employing one or morebackside inserts 90, it will often be advantageous to ensure that thesecuring hardware 60, the backside inserts 90, and the backside recess88 are configured such that, during thermal loading, with the securinghardware 60 and backside insert 90 in an engaged state, the backsideinsert is able to move with the securing hardware within the backsiderecess without dislodging from the recess. For example, referring to theembodiment of the present disclosure illustrated in FIGS. 10-11, where arefinement of the undercut embodiment illustrated above with referenceto FIGS. 8A-8C is illustrated, the backside insert 90 is provided withtabs 95 that are configured to complement the undercut portions 89formed in the electrode material of the showerhead electrode 80. Theinsert 90 can be secured in the recess 88 by aligning the tabs 95 withthe corresponding grooves 85 in the electrode 80, inserting the insert90 in the recess 88, and rotating the insert 90, as defined by thegrooves 85.

In the embodiment of FIGS. 10 and 11, the insert 90 can be secured inthe recess 88 in a spring-loaded state by providing a spring about areduced diameter portion 94 of the buried end 96 of the insert 90 andthe outside diametrical dimensions of the insert 90 and the size andshape of the tabs 95 are chosen to allow for movement of the insert 90in the backside recess 88 in the spring-loaded state. As a result,during the thermal loading typically present in plasma processing, thebackside insert 90 can move with the securing hardware 60 within thebackside recess 88 without dislodging from the recess 88 and withoutdegrading the engagement of the securing hardware 60 and the insert 90.

The present inventors have recognized that any abrasive contact with theelectrode material in the vicinity of the recesses 88 can create asource of potential contamination in the plasma processing chamber 10.Accordingly, where a backside insert 90 according to the presentdisclosure is configured for installation or removal with a screwdriveror other potentially abrasive tool, as is the case in the embodiment ofFIGS. 10-11, it is contemplated that the slotted driving head of thebackside insert 90 can be provided with lateral shielding portions 98 atthe edges of the slot or other engaging portion with which the removaltool is to mate. Stated more generally, the backside insert 90 maycomprise one or more lateral shielding portions 98 configured to permita tool to engage the backside insert at a tool engaging portion thereofwithout extending beyond the periphery of the insert where it could comeinto contact with the inside diameter of the recess in the electrodematerial.

A variety of spring-loaded configurations can be utilized to reduce anytendency of the securing hardware 60 to become disengaged as a result ofstress induced as a result of thermal loading induced during plasmaprocessing. For example, one configuration for providing a spring-loadedengagement of the thermal control plate 70 and the showerhead electrode80 is illustrated in FIGS. 5-7. In FIGS. 5 and 7, the backside insert 90is configured as an anchor in one of the backside recesses 88 formed inthe backside 82 of the showerhead electrode 80 and the securing hardware60 comprises a spring element in the form of a spring-loaded washer 62configured to oppose a force of engagement provided when the securinghardware 60 accesses the backside insert 90. In FIG. 6, the backsideinsert is omitted in favor of direct threaded engagement with a tappedhole in the electrode material. Alternatively, as is illustrated in FIG.9, the spring element can be provided as a helical spring 64 arrangedabout a longitudinal extension of the securing hardware 60 in thesecuring hardware passage 78.

FIGS. 12-14 illustrate a backside insert 110 according to an additionalembodiment of the present disclosure. As is the case with theembodiments disclosed above, the backside insert 110 illustrated inFIGS. 12-14 can be positioned in the backside recesses along thebackside of a showerhead electrode. In the embodiment of FIGS. 12-14,the backside insert 110 comprises a threaded outside diameter 112, athreaded inside diameter 114, and a tool engaging portion 116 formed inthe threaded inside diameter 114. As is the case with the backsideinsert 110 illustrated in FIGS. 10 and 11, the backside insert 110comprises one or more lateral shielding portions 115 between the toolengaging portion 116 and the threaded outside diameter 112 of the insert110. The lateral shielding portions 115 help ensure that a tool engagedwith the tool engaging portion 116 of the backside insert 110 cannotinadvertently extend beyond the threaded outside diameter 112 of theinsert 110. As is noted above, this helps ensure that the tool will notcontact the showerhead electrode and dislodge material from theelectrode as contaminants.

As is illustrated in FIGS. 12-14, the tool engaging portion 116 of thebackside insert 110 comprises a plurality of torque-receiving slots 120arranged about the axis of rotation 130 of the backside insert 110. Tohelp ensure that users do not attempt to remove the inserts withconventional tools, like flat head and Phillips head screw drivers, thetorque-receiving slots 120 are arranged such that attempts to engageopposing pairs of torque-receiving slots 120 with, for example, a flathead screw driver, would result in a cumbersome off-axis rotation of theinsert 110. More specifically, as is illustrated by the dashed linesextending between opposing pairs of torque-receiving slots 120 in FIG.14, any such engagement between opposing pairs of torque-receivingslots, would be strictly off-axis. In contrast, a complementaryinstallation/removal tool 200 of the form illustrated in FIG. 16, wouldgenerate the more preferred on-axis rotation about the axis of rotation130.

Although FIGS. 12-14 and 16 clearly relate to the case where the toolengaging portion 116 of the backside insert 110 comprises threetorque-receiving slots 120 arranged about the axis of rotation 130 asthree opposing pairs of torque-receiving slots 120, it is contemplatedthat the tool engaging portion 116 of the backside insert 110 maycomprise n torque-receiving slots arranged about an axis of rotation ofthe backside insert as n(n−1)/2 opposing pairs of torque-receivingslots. In FIGS. 14 and 15, the torque-receiving slots 120 are spacedequidistantly about the axis of rotation and n=3 (see FIG. 14) or n=5(see FIG. 15). In alternate embodiments, it is contemplated that thetorque-receiving slots could be spaced equidistantly ornon-equidistantly about the axis of rotation and that, in mostembodiments, it would be preferable to ensure that three, four, or fiveslots 120 are provided (3≦n≦5), as some multi-slot configurations coulddegrade the degree to which on-axis rotation would be avoided.

As is illustrated in FIGS. 12 and 13, the torque-receiving slots 120descend uniformly into the body of the insert 110 without decreasing incross sectional size and, as such, can be described as defining aprogressively non-constrictive cross sectional profile. In contrast,many conventional hardware screw heads, like a Phillips-type screw head,define a cross sectional profile that constricts with depth to helpensure secure engagement of the screw and screwdriver. The presentinventors have recognized, however, that this type of constriction isdisadvantageous in the context of the present disclosure because it canlead to excessive frictional contact between the installation/removaltool and the insert and act as a source of particulate contamination.

To further protect against contamination arising from contact betweenthe removal tool and the backside insert 110, it is contemplated thatthe torque-receiving slots 120 can be designed such that the side walls118 that extend parallel to the axis of rotation 130 are apex-free sidewalls. More specifically, the side walls 118 are free of the abruptgeometrical discontinuities that are typically formed when two linearwall segments connect. These geometrical discontinuities, and thecomplementary counterparts in the matching installation removal tool,can be a significant source of contamination because they typically formrelatively fragile or potentially damaging apexes that can either breakupon contact or dislodge contaminants from a mating surface in themechanical engagement context. As is illustrated in FIGS. 12 and 13,although there could be portions of the slots 120 where a curved sidewall portion connects with a linear side wall portion, the slot designshould be free of linear-to-linear apex-forming connections. As aresult, the installation/removal tool 200, an example of which isillustrated in FIG. 16, can also be designed so that it is free offragile or potentially damaging apexes that are typical oflinear-to-linear side wall connections.

Although the various concepts of the present invention have beendescribed herein in the context of electrode materials such as singlecrystal silicon, polysilicon, silicon nitride, and silicon carbide, itis noted that the present invention has utility in a variety ofcontexts, including those where the electrode material comprises boroncarbide, aluminum nitride, aluminum oxide, or combinations thereof. Inaddition, it is contemplated that the showerhead electrode 80 may bepresented in a variety of configurations without departing from thescope of the present disclosure including, but not limited to, asingle-piece, circular showerhead configurations or multi-component,circular showerhead configurations comprising a circular centralelectrode and one or more peripheral electrodes arranged about thecircumference of the central electrode.

It is noted that recitations herein of a component of the presentdisclosure being “configured” to embody a particular property orfunction in a particular manner are structural recitations as opposed torecitations of intended use. More specifically, the references herein tothe manner in which a component is “configured” denotes an existingphysical condition of the component and, as such, is to be taken as adefinite recitation of the structural characteristics of the component.

It is noted that terms like “preferably,” “commonly,” and “typically,”when utilized herein, are not utilized to limit the scope of the claimedinvention or to imply that certain features are critical, essential, oreven important to the structure or function of the claimed invention.Rather, these terms are merely intended to identify particular aspectsof an embodiment of the present disclosure or to emphasize alternativeor additional features that may or may not be utilized in a particularembodiment of the present disclosure.

For the purposes of describing and defining the present invention it isnoted that the term “approximately” is utilized herein to represent theinherent degree of uncertainty that may be attributed to anyquantitative comparison, value, measurement, or other representation.The term is also utilized herein to represent the degree by which aquantitative representation may vary from a stated reference withoutresulting in a change in the basic function of the subject matter atissue.

Having described the invention in detail and by reference to specificembodiments thereof, it will be apparent that modifications andvariations are possible without departing from the scope of theinvention defined in the appended claims. More specifically, althoughsome aspects of the present invention are identified herein as preferredor particularly advantageous, it is contemplated that the presentinvention is not necessarily limited to these preferred aspects of theinvention.

It is noted that one or more of the following claims utilize the term“wherein” as a transitional phrase. For the purposes of defining thepresent invention, it is noted that this term is introduced in theclaims as an open-ended transitional phrase that is used to introduce arecitation of a series of characteristics of the structure and should beinterpreted in like manner as the open-ended preamble term “comprising.”

1. A showerhead electrode comprising a backside, a frontside, aplurality of showerhead passages, a plurality of backside recesses, anda plurality of backside inserts, wherein: the showerhead electrode is asingle-piece, circular showerhead or a multi-component, circularshowerhead comprising a circular central electrode and one or moreperipheral electrodes arranged about the circumference of the circularcentral electrode; the plurality of showerhead passages extend from thebackside of the showerhead electrode to the frontside of the showerheadelectrode; the plurality of backside recesses are formed in the backsideof the showerhead electrode, the plurality of backside recesses leavinga thickness of electrode material between each of the plurality ofbackside recesses and the frontside of the showerhead electrode; theplurality of backside inserts are positioned in the plurality ofbackside recesses along the backside of the showerhead electrode; eachof the plurality of backside inserts comprise a threaded outsidediameter, a threaded inside diameter, and a tool engaging portion formedin the threaded inside diameter; the tool engaging portion is formedsuch that each of the plurality of backside inserts further comprisesone or more lateral shielding portions between the tool engaging portionand the threaded outside diameter to prevent a tool engaged with thetool engaging portion of each of the plurality of backside inserts fromextending beyond the threaded outside diameter of each of the pluralityof backside inserts.
 2. A showerhead electrode as claimed in claim 1wherein: the tool engaging portion of each of the plurality of backsideinserts comprises a plurality of torque-receiving slots arranged aboutan axis of rotation of each of the plurality of backside inserts; andthe torque-receiving slots are arranged to avoid on-axis rotation ofeach of the plurality of backside inserts via opposing pairs of thetorque-receiving slots.
 3. A showerhead electrode as claimed in claim 2wherein the torque-receiving slots are defined by apex-free side wallsthat extend parallel to the axis of rotation.
 4. A showerhead electrodeas claimed in claim 2 wherein the hardness of each of the plurality ofbackside inserts does not exceed the hardness of the electrode material.5. A showerhead electrode as claimed in claim 2 wherein thetorque-receiving slots define a progressively non-constrictive crosssectional profile along a direction parallel to the axis of rotation ofeach of the plurality of backside inserts.
 6. A showerhead electrode asclaimed in claim 1 wherein: the tool engaging portion of each of theplurality of backside inserts comprises three torque-receiving slotsarranged about an axis of rotation of each of the plurality of backsideinserts as three opposing pairs of torque-receiving slots; and thetorque-receiving slots are arranged to avoid on-axis rotation of each ofthe plurality of backside inserts via each of the three opposing pairsof torque-receiving slots.
 7. A showerhead electrode as claimed in claim1 wherein: the tool engaging portion of each of the plurality ofbackside inserts comprises n torque-receiving slots arranged about anaxis of rotation of each of the plurality of backside inserts asn(n−1)/2 opposing pairs of torque-receiving slots; and thetorque-receiving slots are arranged to avoid on-axis rotation of each ofthe plurality of backside inserts via each of the n(n−1)/2 opposingpairs of the torque-receiving slots.
 8. A showerhead electrode asclaimed in claim 7 wherein the torque-receiving slots are spacedequidistantly or non-equidistantly about the axis of rotation and 3≦n≦5.9. A showerhead electrode as claimed in claim 1 wherein the plurality ofbackside inserts comprise polyetheretherketone (PEEK) formulated andmanufactured such that the hardness of the plurality of backside insertsdoes not exceed the hardness of the electrode material.
 10. A showerheadelectrode as claimed in claim 1 wherein the plurality of backsideinserts are positioned in the plurality of backside recesses such thatthey are inset relative to the backside of the showerhead electrode. 11.A showerhead electrode as claimed in claim 1 wherein each of theplurality of backside inserts is an anchor in one of the plurality ofbackside recesses formed in the backside of the showerhead electrode.12. A showerhead electrode as claimed in claim 11 wherein each of theplurality of backside inserts is anchored in one of the plurality ofbackside recesses by a threaded portion formed in the electrodematerial.
 13. A showerhead electrode as claimed in claim 1 wherein theelectrode material comprises polysilicon.
 14. A showerhead electrode asclaimed in claim 1 wherein the electrode material comprises siliconnitride.
 15. A showerhead electrode as claimed in claim 1 wherein theelectrode material comprises silicon carbide.
 16. A showerhead electrodeas claimed in claim 1 wherein the electrode material comprises boroncarbide.
 17. A showerhead electrode as claimed in claim 1 wherein theelectrode material comprises aluminum nitride.
 18. A showerheadelectrode as claimed in claim 1 wherein the electrode material comprisesaluminum oxide.
 19. A showerhead electrode comprising a backside, afrontside, a plurality of showerhead passages, a plurality of backsiderecesses, and a plurality of backside inserts, wherein: the plurality ofshowerhead passages extend from the backside of the showerhead electrodeto the frontside of the showerhead electrode; the plurality of backsiderecesses are formed in the backside of the showerhead electrode, theplurality of backside recesses leaving a thickness of electrode materialbetween each of the plurality of backside recesses and the frontside ofthe showerhead electrode, and the electrode material comprisespolysilicon, silicon nitride, silicon carbide, boron carbide, aluminumnitride, aluminum oxide, or combinations thereof; the plurality ofbackside inserts are positioned in the plurality of backside recessesalong the backside of the showerhead electrode; each of the plurality ofbackside inserts comprise a threaded outside diameter, a threaded insidediameter, and a tool engaging portion formed in the threaded insidediameter; the tool engaging portion of each of the plurality of backsideinserts comprises a plurality of torque-receiving slots arranged aboutan axis of rotation of each of the plurality of backside inserts; andthe torque-receiving slots are arranged to avoid on-axis rotation ofeach of the plurality of backside inserts via opposing pairs of thetorque-receiving slots.
 20. A showerhead electrode comprising abackside, a frontside, a plurality of showerhead passages, a pluralityof backside recesses, and a plurality of backside inserts, wherein: theplurality of showerhead passages extend from the backside of theshowerhead electrode to the frontside of the showerhead electrode; theplurality of backside recesses are formed in the backside of theshowerhead electrode, the plurality of backside recesses leaving athickness of electrode material between each of the plurality ofbackside recesses and the frontside of the showerhead electrode, and theelectrode material comprises polysilicon, silicon nitride, siliconcarbide, boron carbide, aluminum nitride, aluminum oxide, orcombinations thereof; the plurality of backside inserts are positionedin the plurality of backside recesses along the backside of theshowerhead electrode; each of the plurality of backside inserts comprisea threaded outside diameter, a threaded inside diameter, and a toolengaging portion formed in the threaded inside diameter; the toolengaging portion of each of the plurality of backside inserts comprisesn torque-receiving slots arranged about an axis of rotation of each ofthe plurality of backside inserts as n(n−1)/2 opposing pairs oftorque-receiving slots; the torque-receiving slots are arranged to avoidon-axis rotation of each of the plurality of backside inserts via eachof the n(n−1)/2 opposing pairs of the torque-receiving slots, define aprogressively non-constrictive cross sectional profile along a directionparallel to the axis of rotation of each of the plurality of backsideinserts, and comprise apex-free side walls that extend parallel to theaxis of rotation.